Fluid distributor and device for treating a fluid such as a chromatograph equipped with said distributor

ABSTRACT

The invention relates to a fluid distributor, particularly for a chromatography apparatus of large diameter in relation to its height. 
     The distributor (2) comprises a separator (20) consisting of a disc of porous material, and a distribution plate (21) comprising, on its face in contact with the separator, annular channels (29 to 33) connected to a feed or discharge line by conduits (34 to 43) whose dimensions are calculated in order to introduce, in operation, a pressure drop which is inversely proportional to the area of the corresponding channel, measured on its surface of the separator.

The present invention relates to a fluid distributor, intended to ensurea uniform distribution of pressures and flow rates in the cross-sectionof a stream of the said fluid, as well as to a device for treating afluid, equipped with a distributor of this kind, and employedparticularly in chromatography.

Chromatographic techniques are at present enjoying an increasingsuccess, in particular those according to which a liquid is passedthrough a mass of beads of porous material, in order to separate thecomponents present in this liquid. Among the most important applicationsthere may be mentioned blood treatment, as well as many processes in thefield of biotechnologies. Progress in the methods leads to the use ofchromatography columns of increasing size, capable of reaching adiameter of the order of 1 meter, and a height of 0.9 meter. Thematerial required for chromatography, which, in the case of lowpressures, is made up of beads 20 to 200 micrometers in diameter, madeof spongy gelatine, and, in the case of high pressures, of silicaparticles of similar shapes and dimensions, is very costly. It musttherefore be employed as efficiently as possible and this means that thedistribution of the stream of fluid through these large columns must beas uniform as possible.

Chromatography columns usually consist of a vertical cylindricalenclosure, generally made of glass, closed at its lower and upper endsby a distributor comprising a separator consisting of a plate of porousmaterial with open porosity, for example sintered polypropylene, and adistribution plate which rests on the separator and comprises at leastone channel on its side facing the separator, this plate being crossedby at least one conduit connecting the said channel, or the saidchannels, to a single feed channel situated on the opposite side.

In the most commonplace embodiment, such as described in patent GB-A-2085 614, the conduit is central, and the channels go out diverging fromthe centre towards the periphery, branching, so as to offer,substantially over the whole surface of the plate, an approximatelyconstant ratio between the areas devoted to the flow of fluid and thoseused to support the separator. The depth or the width of the groovesmust increase on approaching the centre, so as to ensure a uniform flowof liquid. As a result of this, production of such components, which isusually performed by moulding, is very costly. In fact, the machining ofa suitable mould in a highly resistant steel is difficult to obtain andrequires much time and care. An imperfect mould results in defects inthe plate, which can give rise to cleaning difficulties.

The objective of the present invention is to provide a distributor inwhich the production of the distribution plate is much simpler and whosecost of manufacture is much more reasonable.

Another objective of the invention is to provide a device for treatingfluid, such as a chromatograph, in which the disassembly operations andadjustments are easy and quick.

To obtain this result, the invention provides a fluid distributorintended to ensure a uniform distribution of the pressures and flowrates over the cross section of a stream of the said fluid, thisdistributor comprising a separator (20) consisting of a plate of porousmaterial with open porosity and a circular distribution plate (21)bearing on the separator comprising at least one open channel on itsside facing the separator, and being crossed by at least one conduitconnecting the said at least one channel to a single feed or dischargeline situated on the opposite edge, said at least one conduit (34-43)connecting the said at least one channel to the feed or discharge lineintroducing, in operation, a pressure drop between the said line and thecorresponding channel, which is inversely proportional to the area ofthe corresponding channel, measured over the surface of the separator,characterized in that said channels are circular and concentric, said atleast one conduit connecting said channels to the feed or discharge linecomprising star-shaped grooves (34, 36, 38, 40, 42) hollowed out in theside of the distribution plate which faces away from the separator,these grooves being covered by a support plate (5) in contact with thedistribution plate, said at least one conduit additionally comprisingpassages (35, 37, 39, 41, 43) perpendicular to the distribution plate,opening into a groove on the one side and into a channel on the otherside.

Avantageously, the cross-section of these passages is smaller than thegrooves into which they open out.

Here again, it can be seen that a shape which is simple and easy toobtain is involved. It will be noted that it is not necessary for thedepth of the grooves to vary as they move away from the centre, or evento vary from one groove to another, since the pressure drop is obtainedchiefly with the aid of the passages which pass through the plate.

According to an advantageous form, the passages are provided withinterchangeable nozzles to permit the pressure drop in the correspondingconduit to be adjusted. Using the same single plate it is thus possibleto allow for different viscosities of the fluids to be treated.

The areas of the channels of the distribution plate are advantageouslyequal to each other and the pressure drops introduced by the conduitsare equal to each other.

To obtain a device for treating a fluid, such as a device for treatmentby chromatography, a cylindrical enclosure is advantageously provided,which is closed at its ends by two distributors of the above type, thesedistributors being arranged with their separation facing.

To make it easier to dismantle and adjust the dimensions of an enclosureof this kind, it has been found advantageous for the distributor to befastened to a support plate provided with an inflatable seal ensuringsealing to the side wall of the enclosure.

In the devices of the prior art, the sealing between each distributorand the side wall of the enclosure is obtained by squashing an O ring. Asolution of this kind is difficult to apply in the case of largediameters because considerable forces must then be provided to squashthe O ring in a suitable manner and/or very high accuracy must beprovided in the diameter of the distributor and of the inner wall of theenclosure. Moreover, even a small obliqueness of the plane of thedistributor relative to the axis of the enclosure can make the sealingfaulty. The use of a suitable seal does not involve large forces. Inaddition, its great distortion latitude permits much greater dimensionaltolerances.

In order to obtain an inflatable clamping of the mass of chromatographicmedium which fills the space included between the two separators, in achromatograph of large diameter arranged vertically, it isadvantageously provided for the upper distributors to be fastened to aplate which can be carried by a central supporting rod, with a clearancewhich corresponds to the compressibility of the mass of chromatographmedium, and vertical tamping rods arranged near the periphery of thisplate provide the desired and uniform clamping of the said mass.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in a more detailed manner with theaid of a practical example, illustrated with the aid of the drawings,among which:

FIG. 1 is a partially sectioned general view of a chromatography columnin accordance with the invention,

FIG. 2 is a partial section, on a larger scale, of a distributoraccording to the invention,

FIGS. 3 and 4 are partial views from above and from below respectively,of the distribution plate of the distributor of FIG. 2.

FIG. 5 represents a preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The chromatograph described in the figures is an apparatus of largesize, with a diameter of approximatively 450 mm, this size being givenby way of example, and of comparable height. Such equipment is employedfor separating a component from a liquid, for example the separation ofthe serum present in blood. The low value of the height/diameter ratioobviously demands a very good distribution of the liquid flow over thewhole cross-section.

The chromatograph, which can be seen as a whole in FIG. 1, comprises acylindrical tube of revolution 1, arranged vertically, an upperdistributor 2, and a lower distributor 3, with the volume 4 defined bythese two distributors forming the working chamber, which is filled witha mass of beads of porous gelatine, which forms the separating materialin this case.

The upper distributor 2 is fastened to a support plate 5 and forms withit a plunger which can move inside the tube 1, and this allows itsposition to be adapted to the exact volume of the beads placed in thevolume 4. Tamping rods 6, distributed uniformly along the periphery ofthe support plate 5, allow a suitable pressure to be exerted on the massof beads. These tamping rods bear, by virtue of a threading, on an upperend plate 7 mounted on top of the tube 1. The end plate 7 is itselfconnected to a lower end plate 8 by a series of uniformly distributedtie rods 9 arranged outside the tube 1. The lower end plate 8 carriesfeet 10, which support the whole apparatus. When the apparatus isdismantled and reassembled, the weight and the large size of the plungerconsisting of the upper distributor 2 and its support plate make ittricky to handle. To make handling easier, the plate 5 is connected tothe upper end plate 7 by a supporting rod 11, situated in its centralpart, and equipped with a means for manual lifting 12, carried by theplate 7. A safety device, not shown, prevents the rod 11 and the device12 from being subjected to excessive forces when the tamping rods 6 aretightened.

The lower distributor 3 is provided with a support plate 13, identicalwith the support plate 5 of the upper distributor. This support platerests on the lower end plate 8.

Upper 14 and lower 15 positioning rings, through which the tie rods 9pass, hold the glass tube 1 in position relative to the end plates 7 and8. Furthermore, they support a tube 16 made of transparent plastic(methyl methacrylate) concentric with the glass tube 1, which isslightly larger in diameter and which serves both as mechanicalprotection and, if appropriate, as thermal protection, it beingpossible, if appropriate, for a liquid which keeps the temperatureconstant to flow through the volume between the two tubes.

Passing through the upper end plate 7 is a large orifice 16 providing apassage, on the one hand, for a flexible tube 17 for discharging thetreated liquid and, on the other hand, a flexible tube 18 for feedingcompressed air to the seals, as will be seen later. The orifice 16 isalso used to open the upper face of the support plate 5 to theatmosphere.

The end plate 8 has a passage 19 for delivering the fluid to be treatedand a passage 19a for delivering compressed air for the seals. It willbe noted that there is nothing to prevent a reverse direction of travel,that is to say that the conduit 17 can be a delivery conduit and thepassage 19 a passage for discharging the fluid.

Cap seals (not shown) are obviously provided in the appropriate places.

FIG. 2 is a partial, more detailed, cross-section of a preferredembodiment of the upper distributor 2 of its support plate 5 and of theneighbouring components.

The distributor 2 is made up of a separator 20 consisting of a simplecircular plate of sintered polypropylene and of a distribution plate 21consisting of a plate of rigid plastic whose lower face, that is to saythat which is in contact with the separator 20, is shown in FIG. 4. Thislower face comprises projecting parts, all in the same plane, whichprovide the contact with the separator 20, and hollow parts, also all inthe same plane. The projecting parts comprise a circular centralprojection 22 and a series of concentric annular ribs 23, 24, 25 and 26,as well as an edge rib 27. The circular central projection 22, of smalldiameter, occupies approximately 1/1000 of the total surface area of thedistribution plate. The circular ribs 23 to 26 are small in width and,as a group, they make up approximately 1/100 of the total surface areaof the distribution plate. The edge rib 27 is slightly wider and on itsinner edge it is associated with a seal 28.

The projection 22 and the ribs 23 to 27 define between them channels 29,30, 31, 32 and 33 which are limited in their upper part by the body ofthe distribution plate and, in their lower part, by the separator 20. Inradial section, as shown in FIG. 2, their cross-section is rectangular,with a constant height, and a width which depends on the relativeposition of the projection 22 and of the various ribs. The position ofthese ribs and the radius of the projection 22 are calculated so thatthe area of the various channels, measured in the plane of contactbetween the separator 20 and the distribution plate 21 should be thesame from one channel to another. This requires the difference (Re2-Ri2)to be constant for each of the channels, Re and Ri denoting the radiusof the inner edge and of the outer edge of the channel, measured fromthe axis of the distribution plate.

The calculation of the position of the central projection and of thevarious ribs does not present any difficulty from the standpoint ofmathematics. The number of ribs is determined by mechanicalconsiderations and they must, in fact, be sufficient in number to opposeany distortion of the separator 20.

The upper face of the distribution plate 21 is shown in FIG. 3. It isplanar as a whole, but has a series of grooves arranged star-fashion,these grooves being identical in cross-section, but of variable lengths.Four first grooves 34 run from the central region as far as a transversepassage 35 which passes through the plate and open into the bottom ofthe first channel 29 starting from the centre. Four other grooves 36 arelikewise connected to passages 37 opening into the bottom of the secondchannel 30. Similar grooves 38, 40 and 42, of increasing lengths, aresimilarly connected to passages 39, 41 and 43 opening into the followingchannels 31, 32 and 33 respectively. Each group of four ribs of the samelength forms a four-pointed star, so that the passages opening into thebottom of the successive channels are distributed uniformly.

The passages 35, 37, 39, 41 and 43 are not identical with each other.Their cross-section is calculated so that the pressure drop introducedbetween the central dish 44 and the corresponding channel 29 to 33 isthe same for all the channels. Uniform pressure and flow rate conditionsare thus obtained for all the channels, that is to say substantially forthe whole surface of the separator. Very small differences are evenedout by virtue of the permeability of the separator, which acts as adiffuser. The characteristic section of the channels 29 to 33 issufficiently large not to perturb this uniformity. It should beremembered, in fact, that the flow velocities in a chromatographyapparatus are very low.

In the example described, the passages 35, 37, 41 and 43 are simplydrilled through the distribution plate 21. It would also be possible toprovide calibrated constrictions fitted into pre-drilled orifices. Thismore complicated alternative form would make it possible to modify thepressure drops as a function of the working conditions in order alwaysto obtain an optimum equalization of the pressures and flow rates in theseparator and hence in the working volume 4.

The various grooves converge towards the centre into a centraldistribution zone 44 forming a kind of dish. The central projection 22provided on the opposite face serves to prevent excessive mechanicalweakening of this zone.

Near its peripheral edge, the upper face of the distribution plate 21 isprovided with a ring seal 45, similar to the seal 28. Screws 46 passboth through the separator 20 and the distribution plate 21 and arefastened into the support plate 5, which is appreciably thicker. Thissupport plate, which is cylindrical, with a radius substantially equalto that of the distributor 2, is in contact with the upper face of thedistribution plate 21 over the part of its surface which is not occupiedby the grooves or by the central dish 44. In its central part, thesupport plate 5 has a fluid channel 47, arranged axially and opening inthe lower part into a distribution channel 48 which faces the dish 44.

On its peripheral edges, the plate 5 has a circular groove housing aseal 39 consisting of an annular chamber which can be inflated withcompressed air, the compressed air being delivered by means of a conduit50 arranged within the thickness of the plate 5. The dimensions of theseal 49 are calculated so that it can, in any event, ensure a propersealing of the inner volume 4 relative to the exterior, even if theplate 5 were to be slightly oblique relative to the axis. In FIG. 2, theseal 49 is shown in the deflated state. A connecting and anchoringcomponent 51 is fastened by means of screws 52 to the upper face of theplate 5. This component 51 carries an adaptor 53 for the flexible tube17 for discharging the liquid, this adaptor 53 being, of course,connected to the axial passage 47. It also carries an adaptor 54 for theflexible conduit 18, which is used to feed compressed air to theinflatable seal 49 by means of the passage 50. Furthermore, it carriesthe means for anchoring 55 the supporting rod 11. The clearance neededto prevent excessive forces on the rod 11 can be contained in theanchoring device 55, as it can be in the actuating means 12, shown inFIG. 1.

56 shows a component at the end of the tamping rod 6 fitted onto thelatter with a swivel joint and having a surface bearing on the plate 5.

For the sake of simplicity, the lower distributor 3 and its supportplate 13 are absolutely identical with the upper distributor 2 and withits support plate 5. They are merely inverted, the distributor 3 beingabove the support plate 13 and, in the distributor 3, the separatorbeing above the distribution plate. There is therefore no need todescribe them in detail.

The device just described is particularly simple, both in itsconstruction and in its operation, particularly insofar as thedismantling and the reassembly are concerned.

FIG. 5 represents a detail of preferred embodiment of the presentinvention. It is to note that in the above mentioned embodiments, thereis a "dead zone" delimited by the lower part of the inflatable seal 49,the glass tube 1 and the movable plunger, said "dead zone" exhibits thedrawback of never being drained by the liquid flow.

It is particularly a nuisance when several different products arechromatographed one after the other. As a matter of fact, the cleaningbetween two series of different products is not efficient in said "deadzone". Thus, in the embodiment of FIG. 5, holes 60 are made whichcommunicate with the peripheral channel 33 of the distributor and emergevia filter 61 on the lateral wall of the plunger by means of aperipheral rib 62 placed under the inflatable seal 49, thus ensuring alateral distribution of the fluid in said "dead zone", said holes beingdistributed on the whole periphery of the distributor. The advantageresulting will more significant if said lateral distribution is veryclose to the inflatable seal 49. By way of example, the hole diametercan be about 1 mm, but shall not cause significant head losses. On theother hand, according to the invention, the total surface of bothchannels 33 and 33' (33' being the channel emerging on the periphericalrib via filter 61) is equal to the surface of the other channels 29, 30,31, 32.

We claim:
 1. In a fluid distributor intended to ensure a uniformdistribution of the pressures and flow rates over the cross section of astream of the said fluid, this distributor comprising a separator (20)consisting of a plate of porous material with open porosity and acircular distribution plate (21) bearing on the separator comprising atleast one open channel on its side facing the separator, and beingcrossed by at least one conduit connecting the said at least one channelto a single feed or discharge line situated on the opposite edge, saidat least one conduit (34-43) connecting the said at least one channel tothe feed or discharge line introducing, in operation, a pressure dropbetween the said line and the corresponding channel, which is inverselyproportional to the area of the corresponding channel, measured over thesurface of the separator, the improvement wherein said channels arecircular and concentric, said at least one conduit connecting saidchannels to the feed or discharge line comprises star-shaped grooves(34, 36, 38, 40, 42) hollowed out in the side of the distribution platewhich faces away from the separator, these grooves being covered by asupport plate (5) in contact with the distribution plate, said at leastone conduit additionally comprising passages (35, 37, 39, 41, 43)perpendicular to the distribution plate, opening into a groove on theone side and into a channel on the other side.
 2. Distributor accordingto claim 1, wherein said passages have a cross-section which is smallerthan the grooves into which they open out.
 3. Distribution according toclaim 2, wherein said passages are provided with interchangeable nozzlesto permit the pressure drop in the corresponding conduit to be adjusted.4. Distributor according to claim 1 wherein said passages are providedwith interchangeable nozzles to permit the pressure drop in thecorresponding conduit to be adjusted.
 5. Distributor according to claim1, wherein the areas of the channels (29 to 33) are equal to each otherand the pressure drops introduced by the conduits are equal to eachother.
 6. Device for treating a fluid, comprising a cylindricalenclosure (1) closed by two distributors (2, 3), wherein thedistributors are in accordance with one of claims 1, 2, 3, or 4 and arearranged with their separators facing each other.
 7. Device according toclaim 6, wherein in order to facilitate the dismantling and theadjustment of the dimensions of the enclosure, each distributor isfastened to a support plate (3) provided with an inflatable seal (49)ensuring sealing to the side wall of the enclosure.
 8. Device accordingto claim 7 wherein holes (60) are made which communicate with theperipheral channel (33) of the distributor (2) and emerge on the lateralwall of the movable plunger under the inflatable seal (49), said holesbeing distributed on the whole periphery of the distributor.
 9. Deviceaccording to claim 5, said device forming a chromatograph arrangedvertically, in which the volume (4) included between the two separatorscontains a mass of chromatography medium, wherein the upper distributoris fastened to a plate (5) which is carried by means of a centralsupporting rod (11) with a clearance which corresponds to thecompressibilty of the mass of chromatography medium, and verticaltamping rods (6) arranged near the periphery of this plate ensure anappropriate clamping of the said mass.
 10. Device according to claim 6,wherein, in order to facilitate the dismantling and the adjustment ofthe dimensions of the enclosure;said device forming a chromatographarranged vertically in which the volume (4) included between the twoseparators contains a mass of chromatography medium, wherein the upperdistributor is fastened to a plate (5) which is carried by means of acentral supporting rod (11) with a clearance which corresponds to thecompressibility of the mass of chromatography medium, and verticaltamping rods (6) arranged near the periphery of this plate ensure anappropriate clamping of the said mass.
 11. Device according to claim 10,wherein, holes (6) are made which communicate with the peripheralchannel (33) of the distributor (2) and emerge on the lateral wall ofthe movable plunger under the inflatable seal (49), said holes beingdistributed on the whole periphery of the distributor.